High-frequency tuning device



1951 J. D. FUNDERBURG ETAL 2,572,130

HIGH-FREQUENCY TUNING DEVICE Filed Dec. 1, 1949 MM? flaw-22 qy PatentedGet. 23, 1951 UNITED STATES PATENT OFFICE ,5 3 HIGH-FREQUENCY TUNINGDEVICE Joe 1). Fund hul Lo e e and Bur n 1 Heinmil ler, Glendale,Calif., assignors to Gille Bros., Hollywood, Calif., a firm ApplicationDecember 1, 1949, Serial N0.'130,536

(c1. ri -.44)

q e me l The present invention relates to tuned circuits and, moreparticularly, to small, compact and light weight Li C. circuits that areideally adapted for usein the higher megacycle band radio, radar, ortelevision circuits.

It is customary in high frequency circuits to couple a small variablecapacity with a small fixed loop to obtain a tuned circuit. In mostinstances the loop is not tunable so that for differing frequencies theQ of the circuit may not be optimum. Furthermore, the extension of theloop beyond the variable capacity increases the over-all size. of theunit.

It is an, object of the present invention to pro-,, vide an L. C.circuit adapted particularly for high frequency use having both thecapacity and in.- ductance variable. It is. another object of thisinvention to provide an L. C. circuit of minimum space requirements andof wide tuning range.

In broad terms, the invention comprises a variable capacity, preferablyof the interleafed vanetype, surrounded by an open ended (30115111017?ing tube oppositely and partially slotted, with the portions of the tubeseparated by the slots connected to the capacity terminals. Thus, thepath around the slots constitutes the inductance. In case the inductanceis to be made variable, the tube is provided with a shorting ring slidable along the slots to effectively change the extent of the slots,thus providing inductance tuning.

Other objects and advantages of the present invention will be apparentfrom a description of the attached drawings which show a preferred formof the invention as suitable for use in the 225-400 megacycle band offrequencies.

In the drawing:

Figure 1 is a perspective view of a tuned circuit unit embodying thepresent invention.

Figure 2 is an end view in elevation of the unit of Figure 1.

Figure 3 is a fragmentary view partly in section and partly in elevationof the base connection of one side of the inductance shown in Figure 1.

Figure 4 is a longitudinal sectional view of the unit of Figure 1.

Figure 5 is a basal end view in elevation of the device of Figure 1.

Figure 6 is a perspective View of a tuned circuit unit utilizing aslidable slot shorting ring.

Referring to the drawings, a base l of high dielectric, low-lossmaterial such as styrene, for example, is provided with a centralbearing 2 in which a shaft 3 is rotatable. Shaft 3 is provided w t thusua spac mi r ula 9W denser rotor plate 4.

Theinductance is provided by open ended tube In surrounding rotor plates4. Tube I8 is longitudinally slotted, and opposite slots ii extend fromthe base end of tube l0 to terminate just short of the opposite end.Tube Ii] is attached at the slotted end to base I by bolts [2 connectedto the u e at e s de o h s t and b re i3 riveted to the base andextending downwardly adjacent the inside of the opposite side of thetube and soldered thereto. Stator plates l5 are mounted inside the tubeon rods I 3 in position so tha the tor-P a e can b i l a ed therebetweenwhen shaft 3 is rotated. Bearing 2 is connected to the side of tube Hiopposite the one on which the stator blades are mounted, by a threepronged springer washer it, one prong of which rests on base I.

The current path through the tube around the slots forms the desiredinductance, shunted by the variable capacity formed by the rotor andstator plates. However, as it may be desirable to change the value ofthe inductance to maintain a high Q Value in the circuit atsignificantly diiiering frequencies, we prefer to make the in: ductancevariable. This is accomplished by threading the unslotted end of thetube It) to a point Well beyond the end of slots H and by rotating athreaded ring ll on threads [8.

As ring I! is rotated and progressed toward base the ring I! will passand cover the ends of slots H, thus effectively decreasing the length ofthe path around the slots and thus decreasing the inductance of thetube. Thus, both a variation in capacity and in inductance is providedas best shown inFigure 4.

A trimming plate 2B is attached to tube l0 opposite the connectionthereto of spring washer l6. A circuit connection 2| is made on one sideof tube l0, between base I and ring H. The position along the tube ofthe connection 2| may be varied in accordance with the type of vacuumtube and other elements that may be included in circuit.

One unit of the type described capable of tuning from m. c. s. to 320 m.c. s. comprised a brass tube three and one-fourth inches long, one andthree-sixteenths inches inside diameter, slotted for three inches withslot one-half inch wide. The condenser Was of 210 micro-microfaradcapacity. All metal parts of the tuned circuit were silver plated afterassembly. Such a tuned circuit has been found highly satisfactory,

particularly for ease of minor frequency adjustments.

The tuned circuit described is therefore ideally suited for aircraftradio or other mobile radio use where precision tuning, minimum size andweight, and sturdy construction are highly desirable.

It should also be pointed out that there may well be circuits in which asmall precision variable inductance alone is to be used. In this case,the slotted pipe I0, tunable by turning the ring il on threads I8, maybe used with advantage, without including the interiorly mountedvariable capacity. In other instances a fixed interior capacity may beutilized, all tuning being done by turning ring IT.

For extreme accuracy of tuning a slidable split ring Ila may be used inplace of the threaded ring Il, as shown in Figure 6. Here neither theslotted pipe Iii nor the ring lla. are threaded, but the split ring Ilais held in place by friction preferably with the split in the ringpositioned away from either slot. The inner surface of the ring Ilaclosely fits the exterior surface of the pipe Ill and thus accurateshorting is provided by the edge of the ring Ila bridging the slots,when the ring i moved on the exterior surface of pipe II].

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is susceptible of modification in its form, proportions,detail construction and arrangement of parts without departing from theprinciple involved or sacrificing any of its advantages.

While, in order to comply with the statute, the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited to the specificfeatures shown, but that the mean and construction herein disclosedcomprise the preferred form of several modes of putting the inventioninto effect, and the invention is, therefore, claimed in any of itsforms or modifications within the legitimate and valid scope of theappended claims.

We claim:

1. A high frequency tuning device which comprises, in combination, adielectric base member, a bearing sleeve centrally supported in saidbase member, an electrically conductive rotor shaft rotatable in saidbearing sleeve and having a relatively long portion projecting from oneend of said sleeve, a series of electrically conductive rotor plateseach in the form of substantially half of a disc longitudinally spacedalong the projecting portion of said shaft and secured thereon, a seriesof electrically conductive stator supporting rods circumferentiallyspaced on a circle concentric with said rotor shaft and having one endsupported in said base, a hollow cylinder of electrically conductivematerial surrounding said rods and having diametrically opposite slotsextending through the cylinder wall from one end to a point near theother, said cylinder being externally threaded from the shorted endpartway of its length, a shorting bar in the form of an internallythreaded collar of electrically conductive material on the threadedportion of said cylinder movable axially on said cylinder by rotation ofsaid collar, a series of electrically conductive stator plates ofapproximately the form of the rotor plates and concentric therewith buthaving ears along their periphery whereby they are attached to saidrods, said stator plates being longitudinally spaced on said rodsbetween said rotor plates and circumferentially intermediate saidcylinder slots.

2. The combination. in a high frequency tuning device of a hollow metalcylinder having diametrically opposite slots extending through thecylinder wall from one end to a point near the other, an adjustableshorting bar in the form of a metal collar surrounding said metalcylinder and movable axially on said metal cylinder, metalstator-plate-supporting means on the inside of said metal cylindercircumferentially intermediatie said slots, diametrically opposite metalstator plate assemblies secured to said metal stator-plate-supportingmeans, said assemblies each comprising a series of axially spaced metalstator plates each of approximately the form of a semi-disc, a metalrotor plate assembly comprising a series of metal rotor platesapproximately of the shape of the stator plates spaced axiallyintermediate the stator plates, and means to concentrically support therotor assembly within the stator assembly.

JOE D. FUNDERBURG. BURTON P. HEINMIILER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,085,223 Kolster June 29, 193'12,251,631 Mayer Aug. 5, 1941 2,413,451 Johnson Dec. 31, 1946 2,457,816Grimm Jan. 4, 1949 2,483,893 Ecerett Oct. 4, 1949

